1. Field of the Invention
The present invention relates to a device for the galvanic precipitation of aluminum from aprotic, oxygen- and water-free, aluminum organic electrolytes. More particularly, the invention relates to such a device having an electroplating vat which is sealed from the outside and can be charged with a protective atmosphere. The vat has an annularly shaped, closed electrolyte trough and an electrical contacting and support device which can be rotated around a vertical axis within the vat. The support device has support arms radiating outwardly from the vertical axis which support the goods holders and, when the entire device is rotated, guide the holders through the trough. The electrolyte vat further contains a plurality of anode plates which are interchangeably disposed within the electrolyte trough and a charging and discharging fluid lock for the passage of goods holders to and from the electroplating trough. By providing the goods holders with a horizontal transport bar, the goods holders are transported, by an endless chain conveyor which engages with the transport bar, through the charging lock and into the electroplating trough, where it is held by the support arms of the support and contacting device. After treatment, the goods holders may also be automatically removed from the support arms and transported out through the discharging lock on a second endless chain conveyor.
2. Description of the Prior Art
A galvanic precipitation apparatus of this type is described in our earlier German application No. P 30 44 975.3, filed Nov. 28, 1980 which was the basis of a copending U.S. patent application Ser. No. 318,812, filed Nov. 6, 1981 that issued as U.S. Pat. No. 4,363,712 on Dec. 14, 1982. As disclosed therein, in order to prevent the inward diffusion of oxygen and water vapor into the electrolyte when the goods holders are introduced, and to prevent the outward transfer of the electrolyte when the goods holders are removed, the preliminary and main chambers of the charging and discharging lock are connected to one another by a fluid lock filled with an aprotic solvent. The outward transfer of the electrolyte from the electroplating trough upon the removal of the goods carriers is prevented by providing a rinsing zone between the electroplating vat and the fluid lock of the discharging passageway. In this zone, the electroplated goods and the goods holders are cleansed of the electrolyte. The provision of an endless chain conveyor in both of the charging and discharging passageways completes the mechanism and provides a simple and economical loading and unloading of the electroplating vat.
In the earlier application, the goods holders consist of a frame to which the work pieces to be aluminized are secured by electrically conductive support wires. The frame itself is also electrically conductive and is connected to the negative pole of a current source by the support arms of the contacting and supporting device. The various support arms may be separately supplied with an electrical current so that various selected depositing conditions can be set for different work pieces. In addition, the individual support arms can be selectively loaded or unloaded simultaneously or in a specified mechanical manner without interruptions.
The automatic transfer to and from the support arms of the contacting and supporting arms is achieved by providing the goods holders with a transport rod with which hook-shaped dogs of the endless chain conveyors may engage. The ends of the transport rods are designed to serve as support and electrically contacting pegs and are received by the shaped ends located on the forked support arms of the contacting and supporting device.
With commercial electroplating systems, it is necessary that the plate-shaped anodes be replaced from time to time, as they can only be used while they are of a certain thickness. Generally, the replacement of these used anodes does not present a particular problem, as the open shape of the electroplating vats makes them easily accessible. This however is not the case with the electroplating system described in our earlier application, or the ones described in German Letters Patents Nos. 2,537,256 and 2,716,805. With these electroplating systems, an aprotic electrolyte system which has a sensitivity to both moisture and air, is utilized. This sensitivity requires these systems to be closed to air. Thus, the anodes are secured in the electroplating vat prior to the introduction of the electrolyte, and the anodes cannot be replaced so long as the system is in operation.
When such closed, annular electroplating systems were utilized, particularly those using organo-aluminum complex salt electrolytes the replacement of the anode plates was accomplished by removing the electrolyte from the vat and then interchanging the anode plates either after removal of the entire cover system or by using selected openings in the upper cover. This method, particularly in larger systems, was involved and time consuming. Additionally, electrically disruptive coatings were formed on the inside walls of the system due to the unavoidable incursion of air, and these coatings proved difficult to remove.